A switching mode power supply (SMPS) is an electronic power supply that incorporates a switching regulator to convert electrical power efficiently. The SMPS transfers power from a DC or AC source, to DC loads, such as automotive electronics, while converting voltage and current characteristics. Unlike a linear power supply, the SMPS continually switches between low-dissipation, full-on and full-off states, and spends very little time in the high dissipation transitions, which minimizes wasted energy. Voltage regulation is achieved by varying the ratio of on-to-off time. In contrast, a linear power supply regulates the output voltage by continually dissipating power. This higher power conversion efficiency is an important advantage of the SMPS.
There is a common issue with SMPS: the power efficiency is very low when the load current is low because the controller consumes a fixed amount of power regardless of load current. To improve the efficiency in this case, a low power mode operation can be added to shut down function blocks in regular (high power) feedback loop while keeping the output regulated with a simple and low current controller. Low power mode helps to eliminate the power consumption of the regular controller when load current is low. However, the transition from low power mode to high power mode can cause output voltage overshoot or dip if the handover of two modes is not smooth.